This application is based on Japanese Patent Application No. 2001-78095 filed on Mar. 19, 2001, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a fuel pump for supplying fuel from a fuel tank to an internal combustion engine for an automobile and the like. More specifically, the invention relates to reducing and eliminating vapor in the fuel from effecting a flow rate of the fuel.
2. Description of Related Art
In general, fuel pumps for pressurizing and pumping fuel to engines are known in the art. Among them, for example, is one disclosed in Japanese Patent No. 2757646 (corresponding to Koyama et al., U.S. Pat. No. 5,336,045 published on Aug. 9, 1994), which is a fuel pump for pressurizing and pumping fuel to an engine by drawing fuel from a fuel tank and delivering it to a pump channel formed along an outer periphery of an impeller by rotary motion of the impeller. The fuel in each vane groove formed on the outer periphery of the impeller is fed in the impeller""s direction of rotation by rotary motion of the impeller, resulting in fuel pressurization within the pump channel.
In this case, however, vapor may generate in the fuel as a result of an increase in fuel temperature. Consequently, the vapor passes into the vane grooves of the impeller, which hampers the fuel flow rate and subsequently decreases the volume of fuel being discharged from the fuel pump. In addition to the increase in fuel temperature, the drastic change in the flow rate of fuel at the time of drawing fuel from the fuel tank to the pump channel facilitates the generation of vapor in the fuel.
In view of the above-described disadvantages of the prior art, it is an object of the present invention to provide a fuel pump capable of discharging a desired amount of fuel even during the generation of vapor in the fuel. It is another object of the present invention to provide a fuel pump capable of decreasing the generation of vapor. It is still another object of the present invention to provide a fuel pump capable of discharging any vapor being generated.
In order to solve the above problems, the present invention adopts a technical fuel pump feature. That is, an introduction groove of a pump channel has a first vapor chamber formed on a fuel suction port side of the opposite side of a disk-shaped impeller. The first vapor chamber extends outwardly in a radial direction of the impeller. Accordingly, vapor can escape into the first vapor chamber positioned on the outside of the impeller in its radial direction even though the generation of vapor in the fuel within an introduction groove is caused by the rapid change in the flow rate of drawn fuel or the increase in the temperature of fuel. In other words, the introduction of vapor into vane grooves of the impeller can be prevented, allowing a desired discharge amount of fuel by rotary motion of the impeller.
Here, the depth of an introduction groove may be made large, so that a sufficient volume within the pump channel will discharge the desired amount of fuel. An inner wall of a flow channel component may have a curved or tapered surface at a portion where the fuel suction port and the introduction groove communicate with each other, and the depth of the introduction groove is positioned on the fuel suction port side of opposite sides of the impeller and gradually becomes smaller in a rotary direction of the impeller. Accordingly, the fuel drawn from the fuel suction port can be smoothly fed into the introduction groove, so that a rapid change in the flow rate of fuel does not occur. This permits a decrease in the amount of fuel vapor generated and running into the introduction groove.
The introduction groove may have a second vapor chamber formed on the other of the opposite side of the impeller that is on a far side of the impeller from the fuel suction port. The second vapor port extends to a vicinity of an inlet port of the pressurizing groove. The remainder of vapor, which cannot be trapped in the first vapor chamber, can be accumulated in the second chamber positioned above the impeller. Thus, the introduction of vapor into vane grooves of the impeller can be prevented, allowing the discharge of the desired amount of fuel by a rotary motion of the impeller.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.